1. Field of the Invention
The present invention relates to a centrifugal force based microfluidic device, and more particularly, to a microfluidic device which can automatically perform dilution of a sample in a microfluidic structure disposed on a disk type platform, and a microfluidic system including the microfluidic device.
2. Description of the Related Art
Generally, a microfluidic device has a structure including a chamber storing a minute amount of fluid, a channel through which the fluid flows, a valve for controlling flow of the fluid, and various functional units receiving the fluid to perform predetermined functions thereon. A biochip is obtained by arranging such a microfluidic device on a chip-type substrate and is used to analyse the performance of various assays including biologic reactions. In particular, a device that is designed to perform multiple step processes and manipulations using a single chip is referred to as a lab-on-a chip.
A driving pressure is generally required to transfer the fluid within a microfluidic device. Capillary pressure or a pressure generated by a specifically prepared pump is used as the driving pressure. A lab compact disk (CD) or a lab-on a disk is a recently-suggested microfluidic device obtained by arranging microfluidic structures on a compact disk-shaped platform and uses centrifugal force. However, in the case of a lab CD or a lab-on a disk, since a microfluidic structure is not fixed to a frame to revolve, a lab CD or a lab-on a disk is different from a lab-on-a chip, in which a microfluidic structure is fixed to the bottom, in various aspects.
Meanwhile, samples having various concentrations are largely required for chemical or biological experiments. A typical example of this is a calibration for cell counting or quantitative analysis of gene expression. U.S. Pat. Nos. 5,836,004 and 6,705,357 disclose devices which can provide samples having various concentrations on microfluidic chips. However, since electro-osmosis is used in U.S. Pat. No. 5,836,004, a high driving voltage is required. U.S. Pat. No. 6,705,357 cannot provide an exponential function type concentration gradient. In addition, it is difficult to embody the devices on a disk type platform.
Recently, as various centrifugal force based microfluidic devices, which can easily move fluid on a disk type platform, have been developed, there is a need for a device which can automatically provide samples having various concentrations on such a disk type platform.